Question 12

In a co-educational school there are 600 students. Average age of boys is 12 years and that of girls is 11 years. If the average age of all the students is 11 years and 9 months, what would be the number of girls ?

Solution

Let there be g girls in the school.

Number of boys = 600 - g

Total age of girls = g x 11

Total age of boys = (600 - g ) x 12

Total age of the school = 600 x 11.75

But that = 11g + 7200 - 12g

So g = 150

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